Clay structures



United States Patent 3,307,959 CLAY STRUCTURES Ronald H. Cooper, Clare,Mich., assignor to The Dow Chemical Company, Midland, Mich., acorporation of Delaware No Drawing. Filed Aug. 18, 1965, Ser. No.480,749 7 Claims. (Cl. 10667) This invention relates to improved claycompositions and to a method for preparing such compositions. Moreparticularly it is concerned with improved clay compositions which areheat curable stabilized clay structures exhibiting water resistance.

Clay structures prepared according to the known art are formed orextruded from wet clay as a plastic mass. Once formed into the desiredshape, such structures are allowed to air dry and then are fired atappropriate temperatures. This treatment requires many hours andsometimes days for completion. If firing or heat treating of the clay isnot done at an extremely high temperature the molded structure willdisintegrate in the presence of water. Such structures are thereforeuseless for applications which require contact with water.

It is an object of this invention to provide an improved claycomposition useful in producing improved clay structures. It is afurther object of this invention to provide a process for the productionof such improved clay structures. A still further object of thisinvention is to provide a process for the rapid production of claystructures which are water resistant and which may be heated to producea ceramic state with little or no cracking and a minimum of shrinkage.advantages of the process will be readily appreciated and betterunderstood by reference to the following detailed description.

It has now been discovered that a composition comprising clay, amonoasaccharide source material, an alkali metal hydrogen sulfate andwater in the proper proportions, formed or molded to any desired shape,dried at an elevated temperature not substantially in excess of theboiling point of water and heat cured, provides a solid, rigid structurewhich may be prepared rapidly with little or no shrinkage or surfacecracking and which is stable in the presence of water. Such structuremay be heated further to produce ceramic structures in a fraction of thetime previously required and yet retain their size and shape with littleor no cracking.

A wide variety of clays are useful in the practice of this invention andincludes Kaolin clays, Illitic clays, Bentonitic clays and the like. Ingeneral any commercial clay which is plastic when wet and will hardenwhen fired is suitable for use herein.

The binder used to improve such clay compositions according to theinstant invention is a polymeric composition resulting from the actionof an acidic polymerization promoter of monosaccharide source material,preferably empolying an alkali metal hydrogen sulfate as the acidicpromoter. As monosaccharide source material, a monosaccharide sugar,such as glucose or fructose for example, may be used directly ormonosaccharides may be produced in situ by hydrolysis of the readilyobtainable and inexpensive dior polysaccharide hexos sugars as arepresent in cane sugar, beet sugar, molasses, and corn sugar. Thishydrolysis results by utilizing the same acidic material as a hydrolyzerwhich subsequently, at moderately elevated curing temperatures, acts topromote polymerization of the monosaccharide source material.

As acidic salts to promote the hydrolysis and polymerization of themonosaccharides employed herein, any of the known acidic polymerizationagents for monosaccharides may be employed. However, it is preferred touse the alkali metal hydrogen sulfates and the alkali These and otherobjects and ice metal monosubstituted ortho phosphate which arenonvolatile at the elevated curing temperatures, which do not decomposein the temperature range employed and which are solids that are moltenat the curing temperature. Particularly useful materials are the alkalimetal hydrogen sulfates, i.e. sodium bisulfate (NaHSO potassiumbisulfate (KHSO and lithium bisulfate (LiHSO Sodium bisulfate (NaHSObecause of its ready availability, low cost end effectiveness as ahydrolyzer and polymerizing promoter, has been found to be particularlyuseful in the present polymer or resin forming system. The amount ofsaid acid material to be used will vary depending upon the total amountsand types of saccharide sugars present. Highly satisfactory polymericbinders result wherein the ratio of acidic promoter to saccharide variesfrom about 1 to 2 to about 2 to 1. Further, by employing an acid tosaccharide ratio within the range just given, a reduction in curing timeis realized. Lower amounts of acidic polymerization promoter areemployed advantageously when monosaccharides are used directly in thecomposition. Preferably the amount of acid will be about the same as theamount of sugar used, for example, in a clay composition using fromabout 3 to 5 weight percent sucrose a corresponding amount of from about3 to about 5 weight percent NaHSO was used as hydrolyzing andmonosaccharide polymerizing agent.

Relatively low boiling aqueous solutions of acids that possessrelatively large ionization constant (i.e. larger than about 1 10 suchas hydrochloric, dilute nitric, dilute sulfuric, and the like generallyare not useful in the present compositions as hydrolyzers andpolymerization promoters. Some such compounds decompose and some arevolatile at the curing temperature employed and therefore they do notremain in contact with the mixed components for a sifiiciently longperiod to give the needed hydrolysis of polysaccharidesand subsequentacid promoted polymerization of the resulting monosaccharides into thethermoset binder. Likewise, ammonium sulfate, ammonium persulfate,ammonium sulfamate, ammonium acid sulfate, zinc chloride, phosphoricacid, pyrophosphoric acid, monoammonium phosphate and the like are notsuitable for use in the present process and composition as all theseproduce a corresponding volatile acid at curing temperatures.

The ratio between the weight of clay and weight of sucrose employed toproduce the improved products of this invention will vary to some extentdepending upon the characteristics of the clay employed. In someinstances, as little as 1 /2 weight percent of monosaccharides based inthe dry weight of clay may be employed. However, less than 3 weightpercent monosaccharide generally produces a weak clay structure.Quantities of monosaccharides in excess of 15 percent by weight based onthe dry weight of clay produces structures which lose their shape in theinitial firing operation. It is preferred, therefore, to employ fromabout 3 to about 5 percent by weight of monosaccharide based on the clayemployed.

The clay used herein is usually employed in admixture with water. Theamount of water needed will depend upon the characteristics of theparticular clay employed but the water content should be maintained aslow as possible, particularly where pressing of the clay mixtures willbe required to form the desired shape. Usually water contents of from 10to 25 weight percent of the clay are suitable and from 17 to 20 percentby weight of water is usually preferred but preferred moisture contentsare usually dependent on clay type.

Mixing of the components of this composition may be carried out in anysuitable manner. For example, the monosaccharide and acid curing agentmay be added to a predetermined quantity of water to form a solution anddry powdered clay may be added thereto with mixing until a homogeneousmass is produced. Likewise, the monosaccharide and acid curing agent maybe added to a water-containing plastic mass of clay, e.g. such asooutes. At the end of the heating period a product contained surfacecracks and disintegrated in water.

A second specimen prepared in the same way was fired at 980 F. for 16hours. The specimen was very curs in nature with suitable mixing toassure uniform fragile and disintegrated upon handling. products. O nceuniformly mixed, the clay composition An additional specimen wasprepared in a like manner maybe fabricated into any desired shape bymolding, exexcept that such specimen was heated first to 212 F. fortrudlng and the like. The formed composition 1s then 60 minutes, thenheated to 385 F. for 45 minutes. The dried at an elevated temperature,preferably not substanspecimen likewise evidenced surface cracks anddisintially in excess of the boiling point of water, for a periodtegrated i water. Upon heating of a like specimen to of time sufliclentto remove a major portion of the Water 980 F. for 16 hours the productproduced was very weak therefrom. Preferably the drying is conducted ator near a d disintegrated upon handling. 212 F. Once substantially freeof uncombined water, Exam le 3 the formed product is heat cured at atemperature of from about 300 to about 400 F. for a period of time froIn a similar manner to Examples 1 and 2, 150 gram about minutes to about4 hours. The time of cure samples of Kaolin clay were added to 30 gramsof varies directly both with the temperature of cure and the WaterContaining Venous qu tities of sucrose and sothickncss and/0r size ofthe body being cured. If dedium bisulfate as indicated in the tablebelow. The sired, the cured clay composition may then be fi d tcomponents were admixed in a mixmuller for 6 min- 2000 F. or more toproduce a ceramic ti le, 20 utes and specimens were extruded which were3 inches The clay structures prepared by curing the clay comlong and A1inch in diameter. The resultin Specimens position at intermediatetemperatures of 300 to 400 F. W r dri at 212 F- nd then Cur d at 385 F.Some produce a structure with no indication of shrinkage, little sampleswere then fired at higher temperatures. The or no surface cracks, Suchdevi e are trong nd unresults obtained With these specimens are shown inthe affected by water. These structures are suitable for use followingtable TABLE I Composition Wt. Per- Conditions Fired at 2,012 F. for 4hours cent Based on Clay Fired at Fired at mo cs0 F., 1,160 1 16 hours16 hours Drying Curing Tensile Percent Sucrose NaHSOi Time Time RemarkRemarks Remarks Strength Shrinkage Remarks (minutes) (minutes) (p.s.i.)

3.0 3.0 20.0 60 Strong; no Strong; no Very strong; 94 2.13 Strong; no

Surface surface no surface surface cracks; cracks; cracks; cracks;stable in stable in stable in stable in water; no water; no water; nowater. shrinkage. skrinkage. skrinkage.

5.0 5.0 20.0 120 45 do Very strong; 167 8.67 Very strong;

no surface few surface cracks; cracks; stable in stable in water; nowater. shrinkage.

15.0 15.0 20.0 120 60 Very strong 116 19. 26 Very strong;

and hard; some sur no surface face cracks; cracks; stable in stable inwater. water; no shrinkage.

as outdoor roofing or conduit tiles or may be used as stabilized roadsubsurface material as well as use in Various modifications can be madein the present in pottery and the like. If such structures are heatedsuffivention without departing from the spirit or scope thereof cientlyto produce ceramics, the ceramic product is strong for it is understoodthat I limit myself only as defined and contains little or no surfacecracking. in the appended claims.

In order to provide ease in understanding, the follow- I claim: ingexamples are set forth to illustrate the invention but 1. A curable claycomposition consisting essentially are not to be construed to limit thescope thereof. of clay containing from 17 to 20 weight percent water.Example 1.C0mparative (i.e. outside the scope of the from 3 to 5 wglghtpercent of a molfosacchande and invention) from 3 to 5 weight percent ofan alkali metal hydrogen sulfate wherein the Weight ratio ofmonosaccharide to A 1 0 gram S p Of Kaollll R y Was mlXed With alkalimetal hydrogen sulfate is from 1:2 to 2:1. 20 grams of water in annx-muller for six mmu s- Fr m 2. The composition of claim 1 wherein thealkali metal this y mixture a specimen was extruded whi h Was 3 acidsulfate is selected from the group consisting of inches long, 1 inchwide and Mt inch thick. The specimen NaHSO KHSO and LiHSO was heated to385 1?. for 45 minutes and at th n of 3. A curable clay compositionconsisting essentially this period examination showed the product tocontain f k li clay containing fro 17 to 20 Weight r ent :surfacecracks. Upon immersion in water the specimen water, from 3 to 5 weightpercent sucrose and from 3 disintegrated. to 5 weight percent NaHSOwherein the weight ratio A second specimen prepared in the same fashionwas f r e to NaI-ISO i about 1:1, additionally fired at 980 F. for 16hours. After firing 4. A process for the rapid production of astabilized the specimen was very weak and distinguished upon hanclay trt hi h comprises dling. (1) admixing clay with from 10 to 25 weight per=Example 2.-C0mparative cent water, 1.5 to 15 weight percent of amonosac- A clay specimen was prepared according to the procechange andfrom to 15 Weight Percent an dure of Example 1 except that 5 percent byweight based alkfill metal hydrogen SPIfate Whefeln fh h on the claycontent of sucrose was added to the formularatlo 0f the moflosaccharldet0 the alkali metal y tion. The specimen was heated to 385 F.-for 45mindrogen sulfate 15 from 2:1 to 1:2,

(2) drying such mixture at an elevated temperature not substantially inexcess of the boiling point of water, and,

(3) curing said dried mixture at a temperature of 300 to 400 F.

5. A process for the production of a stabilized clay structure whichcomprises 1) admixing clay with from about 17 to 20 weight percentwater, from 3 to 5 weight percent of a monosacoharide, from 3 to 5weight percent of an alkali metal hydrogen sulfate selected from thegroup consisting of NaI-ISO' KHSO and Lil- S0 wherein the weight ratioof monosaccharide to alkali metal hydrogen sulfate is from 2:1 to 1:2,

(2) forming said mixture into a shape,

(3) drying said formed shape at about 212 F., and

(4) curing said dried formed shape at a temperature of from about 300 to400 F. for a period of time of from 30 minutes to 4 hours.

6. A process for the production of a stabilized clay structure whichcomprises 1) admixing kaolin clay with from about 17 to 20 weightpercent Water, from 3 to 5 weight percent sucrose and from 3 to 5 weightpercent NaHSO wherein the weight ratio of sucrose to NaHSO is about 1:1,

(2) forming said mixture into a shape,

(3) drying said formed shape at about 212 F., and

6 (4) curing said d-ried formed shape at a temperature of from about 300to 400 F. for a period of time from 30 minutes to 4 hours. 7. A processfor the production of a stabilized ceramic 5 structure which comprises(1) admixing kaolin clay with from about 17 to 20 weight percent water,from 3 to 5 weight percent sucrose and from 3 to 5 weight percent NaHSOwherein the weight ratio of sucrose to NaHSO is about 1:1,

(2) forming said mixture into a shape,

(3) drying said formed shape at about 212 F.,

(4) curing said dried formed shape at a temperature of from about 300 to400 F. for a period of time from 30 minutes to 4 hours, and

(5) additionally curing said dried formed shape at a temperature ofabout 2,012 F. for a period of time sufficient to produce a ceramicstructure.

References Cited by the Examiner UNITED STATES PATENTS 2,480,577 8/1949Hertzell et a1. 10667 2,965,504 12/1960 Gogek 106-71 25 TOBIAS E. LEVOW,Primary Examiner.

HELEN M. MCCARTHY, J. E. POER,

Assisan t Examiners.

1. A CURABLE CLAY COMPOSITION CONSISTING ESSENTIALLY OF CLAY CONTAININGFROM 17 TO 20 WEIGHT PERCENT WATER, FROM 3 TO 5 WEIGHT PERCENT OF AMONOSACCHARIDE AND FROM 3 TO 5 WEIGHT PERCENT OF AN ALKALI METALHYDROGEN SULFATE WHEREIN THE WEIGHT RATIO OF MONOSACCHARIDE TO ALKALIMETAL HYDROGEN SULFATE IS FROM 1:2 TO 2:1.